How is carbon 14 used in radiocarbon dating
In 1949, American chemist Willard Libby, who worked on the development of the atomic bomb, published the first set of radiocarbon dates.
More recently is the radiocarbon date of 1950 AD or before present, BP.
Long tree-ring sequences have been developed throughout the world and can be used to check and calibrate radiocarbon dates.
An extensive tree-ring sequence from the present to 6700 BC was developed in Arizona using California bristlecone pine (), some of which are 4900 years old, making them the oldest living things on earth.
Radiocarbon is then taken in by plants through photosynthesis, and these plants in turn are consumed by all the organisms on the planet.
So every living thing has a certain amount of radiocarbon within them.In a stratigraphical context objects closer to the surface are more recent in time relative to items deeper in the ground.